Solid lubricant coating for fluid pump or compressor
Reference Number: N 01-02
Inventors: Rao, V. Durga N.; Fucinari, Carlo A.
Invention SummaryIt is an object of this invention to provide a fluid pumping apparatus that has relatively-moving internal parts constituted of a light weight material, such as aluminum or magnesium, to promote less mass particularly for automotive vehicle applications, while at the same time enhancing pumping efficiency with essentially zero fluid leakage.
In a first aspect, the invention is a high efficiency fluid pump for compressing gases or pumping liquids, the apparatus comprising (a) means for effecting a pumping action by use of relatively movable parts which cyclically move together and move apart at a zone to transfer fluid, the parts being constituted of a light weight material selected from the group consisting of aluminum, magnesium, titanium, copper, bronze, ceramics, such as silicon nitride, cordierire (magnesium aluminum silicate), (b) a coating on at least one of the parts in sufficient thickness to provide essentially zero clearance when said parts have moved together at said zone, the coating comprising solid lubricants in a polymer resin matrix stable up to 700.degree. F. In case of ceramic parts, a thicker coating is applied on a rough machined or as-molded surface and finished by a standard grinding operation. This facilitates very rapid sizing at a substantial savings in process cost, relative to uncoated ceramic parts.
The invention, in another aspect, is a method of making a high efficiency fluid pumping apparatus for gas compressors or liquid transfer, comprising: (a) forming aluminum based relatively movable parts that entrain and effect a pumping action of a fluid, the parts having surfaces that cyclically merge together and move apart to transfer fluid by placing a shear load on such surfaces; (b) machining said surfaces to a finish of 100-150 microns per inch; (c) preparing said rough-machined surfaces by etching or phosphating to effect a dimpled texture; (d) depositing a thin coating on the prepared surface by spraying or rolling, the coating consisting of a mixture of solid lubricant particles and heat curable resin that attracts gas or liquid molecules and is stable up to a temperature of 700.degree. F., the solid lubricant particles having an average particle size within the range of 0.5 to 10 microns, the coating being deposited in a thickness to create a slight interference at said zones; (e) slowly heating the deposited coating to a temperature of about 200.degree. F. and holding said temperature for at least fifteen minutes followed by additional 15 minutes at 375.degree.-400.degree. F.; and (f) after returning the temperature of the coating to room temperature, operating said pump to abrade said coated surfaces to essentially a zero clearance between said relatively moving parts.
An advantage of this invention is an enhancement of pumping efficiency by 5-11% and an increase in pumped volume (density and pressure).